//Code by Patcas Csaba

#include <vector>
#include <string> 
#include <set> 
#include <map> 
#include <queue> 
#include <bitset> 
#include <stack>
#include <list>

#include <numeric> 
#include <algorithm> 

#include <cstdio>
#include <fstream>
#include <iostream> 
#include <sstream> 
#include <iomanip>

#include <cctype>
#include <cmath> 
#include <ctime>
#include <cassert>

using namespace std;

#define LL long long
#define PII pair <int, int>
#define VB vector <bool>
#define VI vector <int>
#define VD vector <double>
#define VS vector <string>
#define VPII vector <pair <int, int> >
#define VVI vector < VI >
#define VVB vector < VB >

#define FORN(i, n) for(int i = 0; i < (n); ++i)
#define FOR(i, a, b) for(int i = (a); i <= (b); ++i)
#define FORD(i, a, b) for(int i = (a); i >= (b); --i)
#define REPEAT do{ 
#define UNTIL(x) }while(!(x)); 

#define SZ size()
#define BG begin() 
#define EN end() 
#define CL clear()
#define X first
#define Y second
#define RS resize
#define PB push_back
#define MP make_pair
#define ALL(x) x.begin(), x.end()

#define in_file "a.in"
#define out_file "a.out"

#define WRITE_ERROR cout << "ERROR" << endl;
#define WRITE_OK cout << "OK" << endl;


string s;
set<char> valid;

void init()
{
	valid.insert('+');
	valid.insert('-');
	valid.insert('[');
	valid.insert(']');
	valid.insert('B');
	valid.insert('P');
	valid.insert('D');
	valid.insert('I');
	valid.insert('S');
	valid.insert('X');
	FOR(ch, 'a', 'z') valid.insert(ch);
	FOR(ch, '0', '9') valid.insert(ch);
}

bool allValid()
{
	FORN(i, s.SZ)
		if (!valid.count(s[i])) return false;
	return true;
}

int countBaseRegisters()
{
	int ans = 0;
	FORN(i, s.SZ - 1)
		if (toupper(s[i]) == 'B' && toupper(s[i + 1]) == 'P' ||
			toupper(s[i]) == 'B' && toupper(s[i + 1]) == 'X') 
			{
				s[i] = toupper(s[i]);
				s[i + 1] = toupper(s[i + 1]);
				++ans;
			}
	return ans;
}

int countIndexRegisters()
{
	int ans = 0;
	FORN(i, s.SZ - 1)
		if (toupper(s[i]) == 'S' && toupper(s[i + 1]) == 'I' ||
			toupper(s[i]) == 'D' && toupper(s[i + 1]) == 'I') 
			{
				s[i] = toupper(s[i]);
				s[i + 1] = toupper(s[i + 1]);
				++ans;
			}
	return ans;
}

int countLowerCase()
{
	int ans = 0;
	FORN(i, s.SZ)
		if (islower(s[i])) ++ans;
	return ans;
}

bool startsEndsPlusMinus(string s)
{
	return (s[0] == '+' || s[0] == '-' || s[s.SZ - 1] == '+' || s[s.SZ - 1] == '-');
}

bool checkAllExpressions(string s)
{
	if (startsEndsPlusMinus(s)) return false;
	bool ans = true;
	FORN(i, s.SZ - 1)
		if (s[i] == '[')
		{
			int lev = 1;
			FOR(j, i + 1, s.SZ - 1)
			{
				if (s[j] == '[') ++lev;
				if (s[j] == ']') --lev;
				if (lev == 0)
				{
					ans &= checkAllExpressions(s.substr(i + 1, j - i - 1));
					i = j;
					break;
				}
			}
		}
	return ans;
}

int main()
{
	//Read data
	//freopen(in_file, "r", stdin);
	//freopen(out_file, "w", stdout);
	
	init();

	while (getline(cin, s))
	{
		if (s == "") break;
		if (!allValid() || countBaseRegisters() > 1 || countIndexRegisters() > 1)
		{
			WRITE_ERROR
			continue;
		}
		if (countLowerCase() > 1 || startsEndsPlusMinus(s))
		{
			WRITE_ERROR
			continue;
		}
		if (!checkAllExpressions(s))
		{
			WRITE_ERROR
			continue;
		}
		WRITE_OK
	}

	//Solve

	//Write data


	return 0;
}